Rotary bit



April 10, 1934. s',` CAMPBE| 1,954,166

ROTARY BIT Filed July 31, 1931 3 Sheets-Sheet l xx; E291.

/36 27 /a meg April 10, 1934- s. 1.-. CAMPBELL 1,954,166

RQTARY BIT Filed July 51, 1931 5 Sheets-Sheet 2 y my. i

:i i I '/f, l f' :I

nu ff l l l /c 7 i I l: Il

l 6 :Il 5

\ l l 1| 1 Wad f, i: e y

If. We ll, l

/7a :z x "Il f5 v f2 5/ fl V 4 /f /'c' 1? `ll 25.:-

v Inventor.

, /f/ f4 n Patented Apr. 10, 1934 ROTARY BIT Stewart L. Campbell, Berkeley, Calif., assigner to,

John Grant, Los Angeles, Calif.

Application July 31, 1931, serial No. 554,174

12. claims. (Cl. 25a-71) This invention has to do with rotary' bits for well drillingl and similar purposes; and a general object is the provision of a rotary bit of high cut' ting eiiicency, cutting a straight hole,and capable of utilizing various forms of ultimate cutting elements so asto be adapted for efficient action in different types of formations.`

A characteristic feature of the invention lies in its use of a gyratory cutting element acting'upon the lower end of the hole in such manner that, by a gyra-tory movement, it moves around the outer part of the hole, bearing and cutting against the side wall as well as on the bottom. The side thrust occasioned by the localized side contact of the cutting element with the hole wall, is opposed and equalized by a bearing of' the tool body at the opposite side of the hole. This bearing of the tool body may be provided, as I hereinafter explain, in the form of a rolling contact; and with such rolling contact may be incorporated the function of a rolling reamer. And, furthermore, as a specific form of my invention, such rolling contact may be realized in such manner as to control the cutter gyration.

Such characteristics, and'specic exemplications of the invention are explained in detail in the following descriptive matter, and from an understanding of those the invention itself,`and the above stated and further objects, will be best understood. For the purpose of such description of examples, reference is made to the accompanying drawings in which:

Figure 1 is a vertical central section showing a specific form of drill embodyingimy invention;

Figs. 2, 3 and 4 are, respectively, cross lsections taken on lines 2--2, 3 3 and 4-4 of Fig. 1;

Fig. 5 is a central vertical section of another specific form embodying my invention;

Figs. 6 and 7 are, respectively, cross sections taken on line 6--6 and 7-'-7 of Fig. 5; and

Figs. 8 and 9 are, respectively, Views partly in section or partly in elevation, showing the adaptation of other forms of ultimate cutting elements to my invention.

Referring iirst to Figs. 1 to 4 I show therein a bit which includes a mandrel 10 adapted at its v upper end, as at 11, for attachment to a drill stem or `drill pipe for rotation. The mandrel has a lvertical fluid circulation passage 12 through which 'the usual rotary mud is circulated to the cutting element.

In the specic form of the invention shown in these iigures the cutting element 13, here shown end of a cutter spindle 15. The axis of this cutter spindle, and likewise the axes of adapter 14 and cutting element 13, stand at an angle relative to the longitudinal vertical axis of the mandrel and of the tool as' a whole, the spindle being mounted in a bearing 16 which has an angular bearing bore 16a as is clearly shown in Fig. l. Bearing 16 is mounted in the lower end of a rotating cylindric member 17, mounted rotatively upon mandrel 10. The mandrel for this purpose has a cylindric enlargement 18 at its lower end, the cylindric member 17 ts rotatively around that enlargement, and a cylindric nut 19 screws down into the upper end of member 17 and bears upon the mandrel shoulder 18a at the upper end of mandrel enlargement 18. i

. The parts 16, 17 and 19 may, for convenience, be termed the body of the device. Bearing 16 is preferably non-rotatively locked to the cylindric body part 17, as by the set screw shown at 21, so that the two parts 16 and 17 always rotate together relative to the mandrel 10.

Driving connection between mandrel 10 and A cutter spindle 15 may be attained by any suitable interengagement which causes rotation of spindle 15 when the mandrel is rotated, and which at the same time allows gyratory movement of the spindle. For instance, in these drawings, I have shown the upper end of the spindle equipped with a tapered square pin 22 tting into a square socket 23 in the lower end of the mandrel. The fit of these parts may preferably be somewhat less, or the taper of pin 22 is such as to allow the relative angular movement of the spindle which takes place as the spindle gyrates.

Down-thrust of the body and other parts on the mandrel (usually due to nothing more than the weight of the body and the parts supported therein) may be taken care of by the shouldered bearing at 18a. Relative up-thrust of the cutter with relation to the mandrel may be taken care of by any suitable upthrust bearing. For instance the upper end of cutter spindle 1 5 may have an up-thrust bearing face 25 bearing upwardly directly against the lower end of the mandrel.

'Ihe particular cutting element 13 shown in these figures, being a roller cutter, is mounted upon the lower end of adapter 14 in such mannerv as to revolve about the axis of the cutter and of the adapter. Any suitable bearing construction may be used at this point, I show here simply a stud26 depending from the adapter, the roller cutter 13 rotatively mounted on the stud and held on by a nut 27, up-thrust of the cutter on the adapter being taken care of by a shoulderedbearing at 28.' Other types of cutters will, however, require and be given different types of mountings on the adapter or on the cutter spindle 15, as will be apparent.

Cylindric body member 17, in the specific embodiment shown inthe figures now under discussion, is shown as being mounted concentrically on mandrel 10. Its exterior surface may be of any desired formation. For instance, it may or may not have cutting teeth 17a. Preferably I here show it as having such cutting teeth extending vertically o ver the cylindric outer surface of member 17. The provision of such cutting teeth makes of member 17 not only a rolling abutment to bear against the side of the hole and takes the side thrust of the cutter, but also makes of it a rolling reamer which rounds out and straightens the hole cut by the cutting element. f`

Action of the device which has now been described will be best understood from the following considerations. Suppose for the moment that mandrel 10 is rotated at any given speed, say 100 R. P. M. and that member 17 is by some means made to rotate with thev drill stem and mandrel. Cutter spindle 15 and cutting element 13 will then gyrate about the vertical axis of the tool at a gyratory speed equal to the rotational speed of the mandrel. Gyration of the cutter will take place around the central vertical axis of the tool,-

and, if the cutting element 13 were rigidly attached to the cutter spindle, the cutting element would then make no rotation about its own angular axis independent of the gyration. However, in the particular arrangement here shown, where the cutting element 13 is in the form of a roller free to revolve with reference to the spindle, the cutter 13 will roll around on the inside of the hole wall, rolling on the spindle axis in a rotational direction opposite to the rotational direction of the gyration. The rotation of the cutting element with reference to the spindle, at any given speed of mandrel rotation, will then depend upon the radius of the cutting element, the radius of the hole, and the radius of the gyration.

The rolling cutting element such as shown at 13 will preferably have the cutting teeth 13a on its exterior surface, here shown as cylindric, and also cutting teeth 13b on its lower end surface; so that, in rolling around in the bottom of the hole,` the exterior teeth 13a have al rolling action around the side of the hole while end teeth 13b have a milling action on the bottom of the hole. This milling action of such a rotating and gyrat ing cutter is very effective, caused and controlled as it is by both the gyratory movement of the cutter and its rotation about its own axis.

If, on the other hand, body member 17 is by some means held stationary,A so that it does not rotate at all with the mandrel, then bearing 16 is held in one position and the cutter spindle and cutter rotate on what for the time being is a fixed angular axis, without any gyration; and the speed of rotation of the cutter about its an- Cslgular axis is equal to the rotary speed of the mandrel.

Thus, assuming again that the mandrel isbeing rotated at 100 R. P. M., if the body rotates with the mandrel, then the cutter gyrates at R. P. M. and has no rotation about its own axis except that caused by the gyration; but if the body is held against rotation, then the cutter does not gyrate at all but rotates about its own axis in a xecl angular position at 100 R. P. M.

`Between these two extreme conditions, actual operation ofthis form of bit takes place in practice. The body is neither held still, nor does it rotate in synchronism with the mandrel; having, as will now be explained, an action of rolling around the wall of the hole, and therefore having a rotary speed controlled by factors additive'to the speed of mandrel rotation.

The side engagement of cutting element 13, or of any other cutter` so set laterally displaced, causes a reaction side-thrust on the cutter, due to its contact with the side-wall at one side only. 'I'his side thrust forces the Aopposite side of body member 17 against the opposite side of the' hole; and the reaction thrust against the body thus opposes and equalizes the lateral reaction thrust on `the cutter. Thus, as the cutting element gyrates in the bottom of the hole, the body member 17 moves around the side of the hole, keeping its lateral point of contact always opposite the point of lateral contact of the cutter; and the member 17 thus has a tendency to roll on the side wall. This tendency to lroll on the side wall, rather than toy slip frictionally over it, is accentuated by providing the teeth 17a and, in so rolling the teeth 17a have a reaming and hole straightening action. f

Member 17 is preferably of a diameter somewhat less than the diameter of the hole being cut; and the speed at which member 17 rolls around the mandrel axis, at any given mandrel rotation speed, depends upon the relation between the radius of the hole and the radius of the member 17. In any case, however, member 17 tends to rotate about the axis of the mandrel, and to rotate about that axis in a rotational direction opposite to that in which the mandrel is rotated. In so rotating oppositely to the mandrel, member 17 rotatively carries the gyration bearing 16 with it; so that the gyratory speed of spindle 15 is modified, relative to the rotational speed of the mandrel, and, just in proportion as the gyratory speed is so modied, the rotational speed of the cutter about its own angular axis is increased. The result is, in this particular form of device, that the cutter 13 both gyrates and either rolls or rotates; and that the body member 17, acting as a reamer and straightener, rolls around the side of the hole.

In the particular form of cutter shown in Fig.

.1, rolling action of the cutter is attained. If

the cutter be rigidly attached to the driven cutter spindle 15, as for instance is shown in Fig. 8, then the cutter is positively driven in its rotation about the angular cutter axis. 'Ihus in Fig. 8 I have shown the same structure with another type of bit 13d attached to the cutter spindle 15. For purposes of illustration I show a fish-tail bit, although any other type may be used. In fact, the structure here explained lends itself most readily to the use of any suitable type of bit or boring element, as will be readily understood without the necessity of illustrating all possible types of such elements; and by substitution of different types of cutting elements, those which are most eiicient in various forms may at all times be used. And, whatever the type of cutting element, the bit always has both a g., ratory and a rotating action, resulting in the cutting element having both cutting and milling action upon the bottom of the hole, and the bit also having a hole straightening and reaming action.

The bit furthermore has at all times a great tendency to drill a straight hole. The fact that the cutting element constantly presses against one side of the hole while the body element creased over that shown in the gure.

presses against the opposite side of the hole, coupled with the vfact that these two points of contact are always kept opposite in rotation about the hole, tends very forcibly to keep the bit properly aligned and prevents it from working off the true line ofthe hole. In other words, the bit is always laterally tight in the hole; but at the same time ample space is allowed for fluid circulation.

Although fluid circulation passages may be provided in various manners, I show, in the gures under discussion,.a iluid circulation bore 12a through the cutter spindle 15 and forming in effect an extension of circulation bore 12; and a further circulation bore 12b through the adapter 14 forms an` extension which carries the circulating uid directly to cutter 13. The circulation, carryingthe cuttings, then flows upwardly around the cutter and around the body element 17. I have said that the body element 17 is of a diameter less than the diameter of the hole. This relationship not only provides for member 17 rolling around the side of the hole, but also for circulation freedom. The fact that member 17 is of a diameter less than the hole diameter may be expressed in another manner; that the most laterally displaced parts or point of cutter 13 (for instance the edge of cutter 13 at the left in Fig. 1) is displaced laterally from the central vertical axis of the tool further than is the periphery of element 17. This relationship'shows plainly in Fig. 1; and the excess of lateral displacement of the cutter may be, if desired, in-

In other gures I show such an increased relative lateral displacement.

In Figs. 5 to 7 I have shown another form of bit which illustrates the broad principles of my invention, involving gyration of the cutting element and involving opposed side thrusts and rolling action of the body element which may at the same time ream and straighten the hole. Here the mandrel 10c has an eccentrically offset cylindric bearing part 10d, surrounded by a cylindric rolling element 17C, preferably with teeth 17a. The eccentric oifset of the axis of the cylindric element l7c enables it to bear against one side of the hole without being excessively large in diameter, allowing more circulation'clearance at the opposite side, as is clearly shown in Fig. 5. rMember 17o may be held longitudinally on the mandrel by an upper thrust collar and a lower nut 51.

At the lower end of the mandrel the cutter sp'ndle 15o is mounted. Thebearingportion 26e of this4 cutter spindle lies at an angle to the vertical axis of the tool, angling off in a direction opposite to the eccentric lateral projection of rollingelement 17o; so that the cutting element 13e mounted on the cutter spindle will project laterally and oppositely to the projection of l7c and bear against the side of the hole opposite to the side borne against by 17o. 'Ihe type of cutter shown at 13e, is similar to that shown at 13 in Fig. 1, being a rolling cutter which, in the gyratory motion, has a rolling action on the side of the hole and a gyrato-ry and milling action on the bottom of the hole.

'I'he cutter spindle 26e is here shown as preferably mounted in the lower end ofthe mandrel by having a screw-threaded pin 52 t'ted into a corresponding socket 53 in the lower end of the mandrel. The axis of pin 52 is here shown as centered on the eccentric axis of eccentric bearing 10d; but this placement of the pin axis is merely convenient,

due to the relatively small size of the mandrel at that point. In any case, whether the axis of pin 52 coincides with the eccentric axis or coincides with the main vertical axis of the mandrel, the angular offset of the cutter spindle, and thus of the cutter, is suicient to make it project laterally to one side beyond the cylindric element 17e, so that the hole drilled is of a diameter larger than that of 17e and so that the cutter will always bear laterally against one side of the hole and element 17o bear laterally against the opposite side of the hole.

The action in` this bit is similar to that of the bit previously described except that there is no driven rotation of the cutter about its own angularly displaced axis independent of gyration. When the mandrel is rotated the angularly displaced cutter axis gyrates about the mandrel axis, causing the cutter to gyrate about that axis and the axis of the hole, causing the cutter to have the same rolling action which has been previously described. The cutter therefore has a rolling cutting action on the side of the hole and a gyratory milling action on the bottom of the hole.

At the same time the eccentric axis of cylindric member 17o is eccentrically rotated about the center of the mandrel and the center of the hole,

so that the cylindric member 17e also has a gyratory action, its center being rotated about the center of revolution, and the member having a rolling action on the side of the hole.

As in the other form heretofore described, various types of cutters may be substituted for that shown in Fig. 5. For instance, here I again show a sh-tail cutters 13d having a shank 13e with a pin 52a which is screwed up into the mandrel socket 53. The action of such a cutter, or of any other type of cutter substituted, will be readily understood from what has been said before. And I have further illustrated in Fig. 9 how the lateral offset of the cutter may be still further lncreased to make the hole diameter still larger in proportion to the diameter of the rolling cylindric member 17c.

I claim:

1. A rotary drilling tool', comprising a mandrel rotatable about a vertical axis, a bearing sleeve surrounding the mandrel and rotatable thereon about a vertical axis and adapted to bear against one side of the hole being drilled, a cutter carrying spindle journaled in the lower end of the bearing sleeve on an axis laterally offset from the mandrel axis, and a rotary driving connection between the mandrel and the cutter spindle.

2. A rotary drilling tool, comprising a mandrel rotatable about a vertical axis, a bearing sleeve surrounding the mandrel and rotatable thereon about a vertical axis and adapted to bear against one side of the hole being drilled, a cutter carrying spindle journaled in the lower end of the bearing sleeve on an axis angularly laterally olfset from the mandrel axis, and rotary driving connection between the mandrel and the cutter spindle. 1

3. A rotary drilling tool, comprising a mandrel rotatable about a vertical axis, a bearing sleeve surrounding the mandrel and rotatable thereon about a vertical axis and adapted to bear against one side of the hole being drilled, a cutter carryrotatable about a vertical axis, a bearing member mounted on the mandrel and rotatable about a vertical axis and adapted to bear against one side of the hole being drilled, a spindle bearing carried by said bearing member and having a bore, the axis of which is oset laterally from the mandrel axis, a cutter carrying spindle mounted rotatably in said spindle bearing bore, and rotary driving connection between the spindle and the mandrel.

5. A rotary drilling tool, comprising a mandrel rotatable about a vertical axis, a bearing member mounted on the mandrel and rotatable about a vertical axis and adapted to bear against one side of the hole being drilled, a spindle bearing carried` by said bearing member and having a bor, the axis of which is offset angularly laterally from the mandrel axis, a cutter carrying spindle mounted rotatably in said spindle bearing bore, and rotary driving connection between the spindle and the mandrel.

6. A rotary drilling tool, comprising a mandrel rotatable about a vertical axis, a bearing on the mandrel extending to one side thereof approximately the radius of the hole being drilled and extending to the opposite side a lesser distance, a cutter rotatively connected to the mandrel below said bearing and extending outwardly to said opposite side of the mandrel axis approximately the radius of the hole being drilled, and extending to the first mentioned side of the mandrel axis to a lesser distance, so that the cutter moving about the mandrel axis engages only one side of the hole and said bearing moving about the mandrel axis engages only the opposite side of the hole.

7. A rotary drilling tool, comprising a mandrel rotatable about a vertical axis, a rotating bearing sleeve of diameter less than the hole being drilled mounted on the mandrel on an axis offset to one side of the axis of mandrel rotation, so that the rotating bearing sleeve contacts with one side onlyof the hole, and a rolling cutter rotatively connected to the mandrel on an axis offset to the opposite side of the axis or mandrel rotation,

the diameter of the roller cutter being such that it projects, at the side of the mandrel axis on which its axis is offset, a distance"- substantially equal to the projection of the bearing sleeve at the rst mentioned side of the mandrel axis of rotation; all so that the bearing-sleeve and the roller cutter gyrate in opposing relation about the mandrel axis ofrotation and the bearing sleeve and Icutter engage only opposite sides of the hole.

8. A rotary drilling tool, comprising a mandrel rotatable about a vertical axis, a bearing on the mandrel extending to one side thereof approximately the radius of the hole being drilled and extending to the opposite side a lesser distance, a cutter mounted on the mandrel below the bearing and extending angularly outwardly to said opposite side of the mandrel axis approximately the radius of the hole being drilled, and extending to the rst mentioned side of the mandrel axis to a lesser distance, so that the cutter moving about the mandrel axis engages only one side of the hole and the bearing moving about the mandrel axis engages only the opposite side of the hole.

9. A rotary drilling tool, comprising a mandrel rotatable about a vertical axis, a rotating bearing sleeve ofdiameter less than the hole being drilled mounted on the mandrel on an axis offset to one side of the axis of mandrel rotation, so that the rotating bearing sleeve contacts with one side only of the hole, and a rolling cutter carried by the mandrel on an axis angularly offset to the opposite side of the axis of mandrel rotation, the diameter of the roller cutter being such that it projects, at the side of the mandrel axis on which its axis is offset, a distance substantially equal to the projection of the bearing sleeve at the rst mentioned side of the mandrel axis of rotation; all so` that the bearing sleeve and the roller cutter gyrate in opposing relation about the mandrel axis of rotation and the bearing sleeve and cutter engage only opposite sides of the hole.

l0. A rotary drilling tool, comprising a mandrel adapted to be connected to a drill pipe and rotatable about a vertical axis, a cutter mounted on the mandrel, offset laterally from the mandrel axis so as to gyrate when the mandrel is rotated and protruding laterally to one side of the mandrel to bear against one side of the hole being drilled, a bearing sleeve rotatably mounted on the mandrel below the drill pipe and adapted to bear against the opposite side of the hole being drilled, a pair of axially spaced annular shoulders on the mandrel, and a pair of oppositely facing shoulders on the bearing sleeve engaging the first mentioned shoulders to prevent axial movement of the sleeve on the mandrel in either direction.

l1. A rotary drilling tool, comprising a mandrel rotatable about a vertical axis, a bearing sleeve surrounding the mandrel and rotatable thereon about a vertical axis and adapted to bear against one side of the hole being drilled, a cutter carrying spindle journaled in the bearing sleeve ,A on an axis laterally offset from the mandrel axis,

and a rotary driving connection between the mandrel and the cutter spindle.

' 12. A rotary drilling tool, comprising a mandrel rotatable about a vertical axis,aY bearing sleeve surrounding the mandrel and rotatable thereon about a vertical axis and adapted to bear i against the side of the hole being drilled, and a cutter carried by the. sleeve onan axis laterally oiset from the mandrel axis.

STEWART L. CAMPBELL. 

